Method for continuously forming elongated cylinders of polyurethane foam

ABSTRACT

CONTOURING OF FLEXIBLE WEBS OT THE INTERIOR OF AN ELONGATED MOVING MOLDING CHANNEL BY THE PROVISION OF SPECIALLY LOCATED AND SPECIALLY SHAPED GUIDING DEVICES, BY THE PROVISION OF SPECIAL INTERNAL MOLD SUPPORTS AND BY THE SELECTIVE OVERLAPPING OF SEPARATE WEB SHEETS.   D R A W I N G

April 1973 c. FERSTENBERG ,534

METHOD FOR CONTINUOUSLY FORMING ELONGATED CYLINDERS OF POLYURETHANE FOAM5 Sheets-Sheet 1 Filed June 1, 1970 INVENTOR.

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5' Sheets-Sheet 2 Apri 97 c FERSTENBERG METHOD FOR CONTINUOUSLY FORMINGELONGATED CYLINDERS OF POLYURETHANE FOAM Filed June 1, 1970 Aprifi 24,1973 c. FERSTENBERG 3,728,513

METHOD FOR CONTINUOUSLY FORMING ELONGATED Filed June 1, 1970 CYLINDERSOF POLYURETHANE FOAM 5 Sheets-Sheet 3 5 Q Q 7 Q, I k 7 7 7 7 9 (I x J CI C 36 36 46 18E IEQ k 1 Q, [was fasm saee April 1973 c. FERSTENBERG3,729,534

METHOD FOR CONTINUOUSLY FORMING ELONGATED CYLINDERS OF POLYURETHANE FOAMFiled June 1, 1970 5 Sheets-Sheet 4 6244 455 faswwsm April 1973 c.FERSTENBERG 3,729,534

METHOD FOR CONTINUOUSLY FORMING ELONGATED CYLINDERS OF POLYURETHANE FOAMFiled June 1, 1970 5 Sheets-Sheet 5 i EB. I Foo/Y5 122' PIA/V6 r FwvezIN VEN TOR Chum 6'6 Z/BSIF/VEEW Patented Apr. 24, 1973 3,729,534 METHODFOR CONTINUOUSLY FORMING ELONGATED CYLINDERS F POLYURE- THANE FOAMCharles Ferstenberg, Paramus, N.J., assignor to Tenneco Chemicals, Inc.,New York, N.Y. Continuation of application Ser. No. 696,070, Jan. 5,1968. This application June 1, 1970, Ser. No. 41,739

Int. Cl. B2911 27/04 US. Cl. 264-54 4 Claims ABSTRACT OF THE DISCLOSUREContouring of flexible webs to the interior of an elongated movingmolding channel by the provision of specially located and speciallyshaped guiding devices, by the provision of special internal moldsupports and by the selective overlapping of separate web sheets.

production of elongated foamed polyurethane material having a largecontoured cross section, e.g. cylindrical, and an indefinite length; andin this connection the present invention, in one aspect, providesadditions to the subject matter of US. Patents 3,281,894 and 3,296,658,assigned to the assignee of the present invention.

As described in the above-mentioned patents, large diameter cylinders offoamed polyurethane are produced by pouring a liquid reaction mixtureonto a surface, such as a web of sheet material, which moves slowly andcontinuously away from the pouring point in a slightly inclineddirection. During this movement, the web is supported and shaped, as bysegmented conveyors, so that it forms a mold in the configuration of apartially closed cylinder. As the reaction mixture travels along, it issupported in different configurations and passes over different surfaceson which a series of reaction stages occur; and these are manifested ina creaming, a thickening, a foaming, a rising and a solidifying of thereactants, whereby a foamed cellular product having the shape of themold interior is produced at a downstream or output end of the mold. Thethus-produced continuous cylinder is thereafter cut into individuallengths; and these lengths are mounted on machines and rotated against aknife blade which spirally peels them into elongated sheets.

The present invention permits the production of largecross-sectionalfoamed products with a smooth and fissurefree outer surface. In part,the present invention is based upon the discovery that because of themanner in which foam reactants rise, i.e. by a mushroom effect, therising foam itself is not capable of smoothing out wrinkles in the webwhich carries the foam reactants. As a result the rising foam may bridgeover the spaces between inwardly protruding portions of such webwrinkles and entrap air or gas in the intervening spaces. This mayresult in the production of fissures, gas pockets and otherdeformations. Moreover, such deformations would be produced at or nearthe outer surface of the foamed cylinder and thereby result in largematerial losses.

Web wrinkling results from the fact that the web, which is usually ofpaper (although it may be of polyethylene or similar material), is drawnoff a supply roll about which it is wound, in one direction (i.e.longitudinally), and is thereafter bent to curved configuration inanother direction (i.e. transversely). Additionally, the web may berequired to undergo bending in several different planes simultaneously.Because of the limited flexibility and extensibility of the Web, thesecontour changes often result in the production of Wrinkles, therebydeteriorating the quality of the mold to be formed by the web.

The present invention overcomes the above-described web Wrinkle problemby means of novel web guiding arrangements.

According to one aspect of the present invention, a web, for example asheet of chemically treated release paper, is caused to be withdrawncontinuously from a roll and guided along the path of movement of thereacting mixture. Special guide means are provided to change the contourof the paper from an initially flat configuration to curved or otherwisecontoured configurations for shaping the rising foam. The positioningand orientation of each of the various web guiding means is selected tocause the web to undergo contour changes in a manner such thatstretching variations across the web width are eliminated or at leastminimized. This is achieved by guiding the web so as to provide atrajectory for each element across the web Width which is of equal ornearly equal total length as the web moves from a position of onecontour to a position of new contour.

According to a further aspect of the present invention, special innerand outer web support means are provided whereby the web is supportedcontinuously on both sides thereof along substantially its entirelateral extent to prevent buckling and the wrinkles which resulttherefrom. In this connection, it has been discovered that when the webis merely supported externally, as by an outer channel defining support,the web will buckle if the channel is of a size and shape to cause thelateral edges of the web to form upwardly protruding walls ofsignificant height. This buckling problem has been overcome by providinga special internal support of the same general contour as the outersupport so as to define between them a slot-like channel through whichthe web may pass without buckling. The special internal support isspecially configured so that its lower edges rise up just ahead of theupwardly rising expanding foam. Thus all along the foam-forming channelthe web is supported internally in part by the foam and in further partby the internal support.

According to a still further aspect of the present invention, there areprovided a plurality of individual sheets which are combined in a novelmanner to form the overall foam molding web. As illustratively embodied,three separate sheets are provided, including a bottom sheet onto whichthe liquid reaction mixture is poured, and two side sheets which overlapslightly each of the two edges of the bottom sheet. The side sheets areguided along in a simple arc-shaped contour, while the bottom sheetundergoes variations in contour as it passes over a pouring surface, aWeir, and a final configuration surface. Be cause of these transversecontour variations, the edges of the bottom sheet (which is of constantwidth) recede and extend laterally as the sheet moves along. Theseparate side sheets, however, are not affected by contour variationswhich affect the lateral positioning of the edges of the bottom sheet.The lateral movements of the bottom sheet edges are thereby easilyaccommodated and no wrinkles are produced since the overlapping edges ofthe bottom and side sheets easily slide over one another.

Various further and more specific objects, features and advantages ofthe invention will appear from the description given below, taken inconnection with the accompanying drawings, illustrating by way ofexample preferred forms of the invention.

FIG. 1 is a plan view, partially cut away illustrating the main portionof a foam molding apparatus in which the present invention is embodied;

FIG. 2 is a side elevational view, also partly cut away, of the foammolding apparatus of FIG. 1;

FIG. 3 is an enlarged fragmentary view of a portion of the foam moldingapparatus as shown in FIG. 2;

FIG. 4 is an enlarged cross-section view, taken along line 44 of FIG. 2;

FIG. 5 is an enlarged cross-section view taken along line 5-5 of FIG. 2;

FIG. 6 is a fragmentary perspective view of the input portion of thefoam molding apparatus of the preceding figures;

FIG. 7 is a perspective view illustrating a weir structure used in thesystem of FIGS. 1-6; and

FIGS. SA-B and FIGS. 9A-B are diagrammatic views illustrating the mannerin which web wrinkling is avoided by the novel web guiding arrangementsof the present invention.

In the foam molding apparatus shown in FIGS. 1 and 2, liquid reactants10, such as those described in the aforementioned patents, are poureddown through a nozzle 12 onto a support surface 14, and are moved alongon the support surface while they react to form a cellular foamedproduct 16. The surface 14 is formed by a paper web 18. The web 18 is acomposite made up of a bottom sheet 18a and two side sheets 18b and 18c.The sheets making up the web 18 may be of paper; and they are treatedwith a coating which serves to permit release of the foamed product 16after completion of the molding operation.

The bottom sheet 18a is withdrawn from a supply roll (not shown) bymeans of a pair of driven pinch roll 20. The sheets pass along through aportal 22 and under the nozzle 12. The portal 22 is a structure whichserves to support the nozzle 12 and the various piping and otherequipment appurtenant to it. From the nozzle, the sheet proceeds throughan entrance guide 23 and over a weir structure 24. From there it movesalong through a molding channel 26.

The molding channel 26 is made up of an endless loop bottom conveyor 28(FIG. 1), and a pair of side conveyors 30. The bottom conveyor 28 is offlat contour and provides bottom support for the molding channel. Theside conveyors 30, as shown in FIG. 1, are provided with a plurality ofadjacent mold segments 32 which cooperate to form a continuous supportfor the web 18. As shown in FIGS. 4 and 5, the segments 32 are shaped asarcs of cylinders along their surfaces defining the molding channel 26.The bottom and side conveyors 28 and are driven in synchronism bysynchronizing driving means 34 so that the channel 26 effectively movescontinuously in the direction of an arrow A away from the nozzle '12.

A stationary internal mold support 36 is provided in the vicinity of theforward ends of the bottom and side conveyors 28 and 30. The internalmold support 36 is generally tubular in configuration; and as can beseen in FIG. 4, it fits closely inside the circular cross-sectiondefined by the cooperating mold segments 32.

Turning now to FIG. 3, it will be seen that the mold support 36 extendsrearwardly only a short distance in complete cylindrical configuration.Beyond this point it is cut away so that it tapers upwardly, firstrather sharply, as indicated at 38, and then more shallowly, asindicated at 40. The upper interior portion of the mold support 36 isbraced by a truss assembly 42. Means (not shown) are provided to suspendthe mold support from above and to 4 hold it in fixed position relativeto the various conveyors 28 and 30;

The weir structure 24, as shown in FIGS. 3, 7 and 8, may be of sheetmetal construction. As shown, it rises up in advance of the moldingchannel 26 to hold back a portion of the liquid reaction mixture untilit has begun to gel.

Turning now to FIG. 6, it will be seen that the front or upstream end ofthe internal mold support 36 encircles the weir structure 24. Asindicated above, the bottom sheet 18a of the web 18 passes over the weirstructure 24. This situation is illustrated in FIG. 6 where the sheet18a is shown to pass over the weir structure and into the mold support36. The bottom sheet 18a is considerably wider than the weir structureitself. Accordingly, the edges of the sheet are bent upwardly to guidethe sheet into the mold support 36. This is accomplished by means of theentrance guide 23. As shown, the entrance guide has lateral guide walls56 and 58 which extend up in advance of and on each side of the weirstructure 24. These lateral guide walls actually form a chute whichforms the bottom sheet 18a into a particular configuration during itsmovement over the weir structure 24.

In FIG. 7 it will be seen that the chute, which is formed by the guidewalls 56 and 58, is initially of trapezoidal configuration. The chutethen tapers inwardly in the downstream direction, and the guide walls 56are of greater length to accommodate the constant Width of the bottomsheet 18a.

Thereafter, in the vicinity of the weir structure 24, the straight guidewalls 56 blend into the curved guide walls 58. Further along, as can beseen in FIG. 6, the guide walls 58 taper outwardly in the downstreamdirection and eventually blend with the curved surface of the moldsupport 36.

Reverting to FIGS. 1, 2 and 6, the outer sheets 18b and are shown to bedrawn from side supply rolls 60 mounted with their axes extending in avertical direction. The sheets 18b and 180 each pass around anassociated guide roll 62. The guide rolls are slightly inclined tochange the direction of motion of the sheets so that they will proceedalong parallel to and in alignment with the sides of the molding channel26.

The side sheets 18b and 180, as shown in FIGS. 1 and 6, pass along theoutside of the guide walls 56 and 58 of the weir structure 24, and alongthe outside of the internal mold support 26. However, they do passthrough arc-shaped slots defined between the mold support 36 and themold segments 32 of the side conveyors 30, as shown in FIG. 4. Thisprovides lateral support on both surfaces of each of the side sheets 18band 180 to prevent them from buckling. Thereafter, downstream of theentrance end of the mold support 36, where it tapers upwardly, the loweredges of the side sheets 18b and 180 come into overlapping contact withthe lateral edges of the bottom sheet 18a, thereby forming the completecomposite web which forms and supports the reacting mixture.

As indicated in FIGS. 1 and 2, the bottom sheet pinch rolls 20 and theside sheet supply rolls 60 are also synchronously driven with theconveyors 28 and 30. This serves to maintain each of the sheets 18a, 18band 180 in uniform movement and to prevent relative movement between anyof the sheets and the conveyors. Thus the imposition of stress andconsequent wrinkling in the sheets is avoided.

In operation of the system, the bottom and side conveyors 28 and 30 andthe bottom sheet pinch rolls 20 and the side supply rolls 60 are alldriven in synchronism through the synchronizing driving means 34. Theliquid reaction mixture 10 is poured out from the nozzle 12 onto thebottom sheet 18a. The liquid runs down toward the weir structure 24 andinto a pool 68. It then passes over the weir and proceeds along downthrough the chan nel 26.

The initial portion of the foam rise is contained by the lateral edgesof the bottom sheet 18a. Eventually, however, the foam rises beyondthese lateral edges; and thereafter the side sheets 18b and 180 serve toprovide the main lateral containment of the foam.

The side sheets 18b and 18c are initially supported fully on both sidesby the mold segments 32 and the internal mold support 36, as shown inFIG. 4. However, as the foam rises, the mold support tapers upwardlyaway from it, as shown in FIG. 3. Thus the regions of the side websvacated by the upwardly tapered internal mold support 36 aresimultaneously occupied by the rising foam itself which presses thesheets out against the outer mold segments 32 before the sheets canbuckle from their own weight and form wrinkles.

It will be appreciated that because of the various configurationalchanges which the bottom sheet 18;: must undergo in passing over theweir structure 24 and into the channel 26, its lateral edges willsequentially project and recede in the lateral direction. This lateralweb movement is easily accommodated in the present arrangement by virtueof the overlapping arrangement between the side and bottom sheets. Theside sheets 18b and 180 thus may proceed along with a continuous curvedcontour and no lateral edge movement, While the lateral edge movement ofthe bottom sheet is readily absorbed in a greater or lesser overlappingof the adjacent sheets. In this manner the complications of transmittinglateral edge movements nearly completely around the girth of the mold,and the consequent production of web wrinkles are avoided.

FIGS. 8A-B and FIGS. 9AB illustrate the manner in which the web handlingarrangement of the present invention operates to reduce or eliminate webwrinkling during changes in its contour. As shown in FIG. 8A, aconventionally guided web 80 moves along between a pair of parallelplanes I and H; and in doing so it changes from fiat to curved contour.The plane I is defined by orthogonal lines X and Y while the plane II isdefined by corresponding orthogonal lines X and Y The path of webmovement is along a third plane III defined by a line Z between planes Iand 11 and the lines X and X During the web movement, its outer edges 82and 84 turn upwardly and inwardly to form the curved contour, while thecenter line 86 of the web proceeds along the center of plane HI.

Turning now to FIG. 8B, it will be seen that the web center line 86reaches plane II before the web edges 82 and 84. As a result of this,the web edges 82 and 84 tend to continue to diverge in an upwarddirection as indicated by the arrows 82a and 8411. In order to cause theweb to proceed along plane III and cause the web edges to follow pathsparallel to this plane, as indicated by the dotted arrow 82b, 84b, itbecomes necessary to stretch the outer web edges by an amount AZ so thatthe entire web cross-section enters plane II at the same time. This,however, produces unequal stretching across the web, with none in thecenter and a great deal along the edges. As a result of this unequalstretching, wrinkles may develop.

FIG. 9A illustrates web guidance in accordance with the presentinvention. Here, instead of changing web contour in plane III, the web80 is caused to proceed initially from a distance Y above plane III andto converge with it as the web contour changes. Thus in this case theweb center line 86 does not reach plane III until it also reaches planeII. With this arrangement, as shown in FIG. 9B, the outer edges 82 and84 will reach plane II at the same time so that the continual path ofmovement for all of the web lines 82, 84 and 86 will be in the directionof the parallel arrows 82b, 84b and 86b. The distance Y is chosen sothat the path of movement of each element across the web width fromplane I to plane II will be of substantially equal length. Knowngometrical methods can be used in ascertaining the displacement Y takinginto account, however, that the outer edges 82 and 84 must undergodisplacements in both the X and Y directions.

The above principles are employed in connection with the modification ofthe contour of the bottom sheet 18a as it passes over variouselevational modifications such as the weir structure 24. As can be seenfrom FIGS. 8A-B and FIGS. 9AB, in order for the moving web to undergochanges in contour without wrinkling, its path of movement must change.That is, where the web edges taper inwardly in the X direction, the webcenter line must change its path of movement in the Y direction. Now inthe case of passing over the weir structure 24, the center line of thebottom sheet 18a will change its path of movement in the Y direction. Inorder to prevent wrinkling, the outer edges of the web must change theirpath of movement in the X direction. That is, the web must taperinwardly. This inward tapering, as shown in FIGS. 6 and 7 is achieved bythe entrance chute walls 56 and 58. Also, as in the previous case, theamount of this taper should be chosen to ensure that each ray orlongitudinal line along the web moves along a path or trajectory whichis as close as possible in length to the path or trajectory of everyother longitudinal line across the web. When this occurs, differentialstresses are minimized and wrinkling is eliminated.

Although a certain specific embodiment of the invention is hereindisclosed for purposes of explanation, further modifications thereof,after study of this specification, will be apparent to those skilled inthe art to which the invention pertains. Reference should accordingly behad to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A method for continuously forming elongated cylinders of polyurethanefoam having a substantially smooth, continuous surface from a liquid,polyurethane foam forming mixture, said method comprising the steps of:

(a) forming a flexible web including a bottom sheet and two side sheets,each side sheet having a bottom edge which overlaps a lateral edge ofsaid bottom sheet,

(b) passing said web into a liquid mixture deposition zone and pouringcontinuously a predetermined charge of said liquid reaction mixture ontothe said bottom sheet in a region substantially intermediate the lateraledges of said bottom sheet,

(c) synchronously moving said sheets longitudinally away from thepouring location and through a web support region and providing in saidsupport region external arcuate lateral support and internal cylindricalsupport for said side sheets and external cylindrical support for saidbottom sheet, and

(d) withdrawing ever increasing amounts of the bottom portion of saidcylindrical support so that the bottom edges of said side sheets assumeoverlapping relationship with the bottom sheet and support the risingpolyurethane foam which bears against said side and bottom sheets andpresses said side sheets against said external lateral outside supportbefore said sheets can buckle from their own weight and form wrinkles.

2. A method as in claim 1 wherein said bottom sheet is transverselycontoured during its longitudinal movement so that the edges undergolateral displacement while still maintaining the overlappingrelationship with the bottom edges of said side sheets.

3. A method as in claim 2 wherein the central portion of said bottomsheet is made to move downwardly during at least a portion of the timethat said cylindrical support thereof is provided, and said edges ofsaid bottom sheet undergo lateral displacement outwardly during saidtime that said central portion is moving downwardly.

4. A method for changing the transverse contour of References Cited anelongated flexible web of sheet material from flat to UNITED STATESPATENTS generally cylindrical while avoiding wrinkle formation in theweb as it moves generally in a longitudinal direction, 3325573 6/1967Boon et a1 18 5 P X 3,496,596 2/1970 Buff 26454 UX send method compnsingthe step of gradually laterally 5 3 093 232 6/1963 Kornylak 26 5 X f d tt I 4 4 s iftmg positions 0 e ge elemen s 1n said web as central3,152,361 10/1964 Edwards 18 4 B elements thereof move perpendicular tosaid longitudinal and lateral directions so that there is substantiallyno I change in the relative longitudinal positions of said ele- PHILIPANDERSON Primary Examiner ments along a transverse section thereof assaid web moves 10 us L X longitudinally, said shifting being such thatedge elements 264 216 313 shift outwardly as center elements movedownwardly.

